Data Quality Feedbackn (DQF) - Help

With the latest release of the LCDB, Landcare Research has also introduced a data quality feedback (DQF) function that will be administered through the LRIS Portal.  DQF is designed to allow LCDB users to report problems or errors in the data set, but go well beyond the existing general comment function.  For example, users can now give specific feedback about incorrect land cover classifications of specific polygons.  The following instructions are aimed at helping first time users follow the DQF process.


One of the new features of LRIS Portal is a satellite imagery background which allows you to see a contemporaneous view of the current land cover which may help to generally orient yourself.  HOWEVER, IT IS REALLY IMPORTANT TO UNDERSTAND THAT THE LCDB WAS NOT MADE USING THIS IMAGERY.  Therefore, any differences between LCDB class and what you see in this imagery do NOT necessarily constitute an LCDB misclassification. 
Unfortunately due to the copyright limitations on satellite data we cannot make the imagery used for creating each version of the LCDB publically available online.  You MUST therefore provide additional evidence other than simply identifying a polygon you believe has the wrong classification based on this background image, and this evidence should include dating information that relates to the dates of LCDB mapping. 

Remember to consider 1 hectare as the recommended minimum mapping unit. 

Identifying LCDB Errors

Let’s follow an example to see how the DQF process works.

In this first image we have zoomed to the western end of the Lake Hawea township where a new sub-division has been constructed over recent years.  First let’s turn on the “satellite with labels” background so we can get some land cover context to the linework in the LCDB dataset.  Choose “Satellite with labels” to get the satellite imagery with street names to assist locating yourself.

Note that you can adjust the transparency of the LCDB polygons to get a better look at the underlying satellite imagery.  Look under the selected items icon and click the drop down icon to the left of the layer name.

Based on local knowledge we now think two polygons in the centre of the image stand out as being out of synch with their background.

In both cases the areas are clearly not exotic forest at the time of the imagery (2014) but have been recorded as forest in all four LCDB dates.

While a possible problem is suspected due to local knowledge, some evidence is required to confirm there may have been an error made.  In this case we’ve turned to Google Earth – but you may well have your own aerial photography or other documentary evidence.

In the lower left of the screen in Google Earth you’ll see a clock icon and date 2005.  This tells us there are several dates of imagery starting in 2005 for this area.  Click on the clock and then hover over the slider that appears in the top left of your screen and it should look like this.

You can now drag the sliders along this bar to see imagery available at different times.  In the first image below in 2004 you can see both the small patch of exotic forest north of Cemetery Road and the more scattered wilding Exotics south of the road.  The area is largely undeveloped for housing.

By April 2007 (below) the subdivision is under construction.  The smaller patch of planted exotic forest north of the road has been substantially reduced in size – but there are still some trees standing, while a substantial part of the larger area of scattered wilding pines to the south of the road has been felled.  It appears that the trees are still lying in the field, but they have browned off considerably suggesting they were felled some time before this image. 

In this final image, May 2011, the small stand of exotic forest north of the road is now entirely felled, and indeed the subdivision now contains 30 or so dwellings, while the felled pines to the south of the road have now been cleared right away and the area returned to pasture/possibly with some broom infestation following the disturbance caused by clearing the pines.

Based on the timing of LCDB imagery 1996-97, 2000-01,  2008,  2012 - we can’t say from this analysis whether the small patch of pines to the north of the road was all felled by 2008 since it was still standing in 2007, but it is definitely gone by 2011 so shouldn’t be exotic forest in LCDB 2012.  In the case of the wilding pines to the south of the road, we can clearly see they had been felled by 2007, so they should not have been recorded as exotic forest in 2008 imagery, and certainly not in 2012.
Now that we have determined there does appear to be an error in the LCDB version 4.0 we can finally initiate a ticket in DQF to submit this error for checking.

Using DQF in the LRIS Portal

The process is relatively simple.   You need to have the LCDB layer turned on and be zoomed into the polygon/area you wish to comment on.   Click on the polygon and bring up the attribute table window showing the attributes for that polygon.

At the bottom of the attribute popup window is a green “submit feedback” button.  Just click on this.

The left hand panel will be replaced with a panel showing you the DQF “ticket” that you have just initiated.  You now need to fill in a subject, a description and you can attach documents or images to the ticket to help us evaluate your error submission.  Note the question mark icons give hover help examples of the type of information we need to evaluate your DQF ticket.  As already stated – please make sure to give clear, concise and accurately dated comments and documentation.

SPECIAL NOTE: the polygon you have selected with its attribute table open will be automatically recorded when the ticket is created – so you don’t need to do anything additional to record the location of your ticket.  When the site administrator opens the ticket they will automatically be panned and zoomed to the ticket location/view.

In terms of what to enter under a ticket - for the example that we are using we might enter the following:

Subject: Hawea outskirts - incorrect LCDB classification for 2008 and 2012

Description: The pine trees in this polygon were felled prior to April 2007 (see attached image from Google Earth) and the LCDB classification for this polygon in 2008 and in 2012 should therefore be low producing pasture. 

Attachments: Attach the Google earth image (or equivalent) by clicking on the “attach image or document” button and browse to the image you’ve saved.  This could instead be a photograph you have taken of a location, but please try to make sure there are locational clues – recognisable buildings or features, and that any photographs you upload clearly show cover type if possible.

As soon as you have entered something in both the Subject and the Description field, you will see that the “Submit Feedback” button along the bottom of the left hand panel will turn green, and you can at any time click on this button to submit your ticket.

This will send an email to the site administrator warning them a new ticket has been created, and you will also now be able to follow the ticket (look in the menu under your username – for my tickets).

You can check on progress with your tickets under your personal menu on LRIS – under your name you’ll find a “My Tickets” option that’ll show you all tickets you have initiated and what their current status is.

NOTE: Response to tickets

At this time we do not anticipate that we will have the resources to respond to tickets “as-they-arrive”.  We expect that we will accumulate tickets for a period of (say) 3 months, and then download all of those tickets for checking and resolution of errors in bursts of intensive effort.  We will endeavour to at least acknowledge receipt – probably by changing ticket status to “on hold”. 

David Pairman,
30 Jun 2014, 19:53